Compounds including a polymerizable group (polymerizable compounds) have been used for producing various optical materials. For example, a polymer having a uniform orientation can be prepared by polymerizing a polymerizable composition including a polymerizable compound which has been arranged in a pattern while being in a liquid crystal state. Such a polymer can be used for producing polarizing plates, phase-difference plates, and the like, which are necessary in the production of displays. The polymerizable composition typically includes two or more polymerizable compounds in order to meet the demands for optical properties, polymerization velocity, solubility, melting point, glass transition temperature, and the transparency, mechanical strength, surface hardness, heat resistance, and lightfastness of the polymer. The polymerizable compounds included in the polymerizable composition are required to enhance physical properties of the polymerizable composition without degrading the other properties of the polymerizable composition.
There has been a demand for phase-difference films having a low- or inverse-wavelength dependence of birefringence in order to increase the viewing angles of liquid crystal displays. Accordingly, various polymerizable liquid crystal compounds having an inverse- or low-wavelength dependence have been developed as a material for such phase-difference films. However, when the polymerizable compounds are added to a polymerizable composition, the polymerizable compounds cause crystals to precipitate, that is, the polymerizable compounds degrade the preservation stability of the polymerizable composition (PTL 3). Furthermore, when the polymerizable composition is applied to a base material and polymerization is subsequently performed, inconsistencies are likely to be formed in the resulting film (PTL 1 to PTL 3). If the film having inconsistencies is used as a material for, for example, displays, nonuniformity in the brightness of the screen and unnatural colors may occur. This significantly degrades the quality of displays. Consequently, the development of a polymerizable liquid crystal compound having an inverse- or low-wavelength dependence, with which the above issues may be addressed, has been anticipated.